iStockphoto(DENVER) -- Colorado’s recently approved gun control laws, passed in response to the Aurora, Colo., and Newtown, Conn., massacres, are being challenged by a delegation of sheriffs who say the laws are unconstitutional.

In March, Colorado Gov. John Hickenlooper signed off on some of the toughest gun control legislation in the country, including a law mandating universal background checks for the purchase of firearms and another restricting the size of high-capacity magazines.

A lawsuit was filed on Friday in Colorado’s U.S. District Court on behalf of 54 of the state’s sheriffs in an effort to block the laws from taking effect.

“This lawsuit is for your rights and for your safety,” Weld County Sheriff John Cooke said at a news conference on Friday.

“These bills do absolutely nothing to make Colorado a safer place to live, to work, to play or to raise a family. Instead these misguided, unconstitutional bills will have the opposite effect because they greatly restrict the right of decent, law-abiding citizens to defend themselves, their families and their homes,” he said.

All but 10 of the state’s 64 sheriffs, who are elected officials, signed their names to the lawsuit.

Tom Sullivan, who lost his son Alex Sullivan in the Aurora movie theater massacre, told ABC News’ Denver affiliate he didn’t understand the backlash to the laws.

“I do not understand why these politicians are picking guns over people,” he said, “and why they want to make it easier for criminals to get guns and for other families to go through what we did.”